A machine such as this is described in DE 698 29 614 T2=EP 0 900 412 B1 (inventor: Erik R. Loopstra et al.) This is a lithography appliance and comprises a frame on which an arm is located, with a radiation source and an optical system (=focusing unit). Furthermore, the machine has a positioning apparatus on which moveable substrate holders are located for the work piece to be processed. Oscillations that occur interfere with the operation of lithography appliances such as these. Oscillation isolation systems are used in order to minimize the influence of oscillations such as these on the machine.
One such oscillation isolation system is disclosed in EP 0 927 380 (Inventors: Erik R. Loopstra and Peter Heiland), and contains air bearings which act vertically and horizontally.
Oscillation isolation systems such as these may be in the form of passive and active systems. In passive oscillation isolation systems, the air bearings react only when oscillations occur, for example of the ground, in order to decouple the machine on oscillation-isolated bearings from the undesirable oscillations. Control systems are additionally used for active oscillation isolation systems. These use sensors to measure the oscillation state of the machine, in order then to pass signals, which counteract the oscillations that have occurred, via actuators to the oscillation isolators. Active oscillation isolation systems such as these make it possible to damp the undesirable oscillations of the machine to be isolated more quickly than is the case when using passive systems.
Appropriate control systems are also used for other moving parts of the overall system, in particular for the robot arm. A plurality of mutually separate control systems are therefore used for an examination or processing machine.
Rough coordination between the individual control systems is achieved by the use of additional host systems, comprising PCs and workstations. In systems such as these, the individual control systems are responsible for controlling the sensor system/actuator system of the respectively associated subsystem in real time, and for carrying out the movement tasks, for example for wafer transportation. The task of the host systems is to determine the times for these movement tasks, and to identify fault states.
One such host system is described, for example, in Korean patent abstracts, publication number 102000041128A, “Wafer Loading Apparatus”. This apparatus has a main control device and a robot control device. The robot control device controls the movements of the robot in all three spatial directions, and signals the results of the control process via an RS232C type interface to the main control device.
If a host system such as this were to be used in conjunction with an active oscillation isolation system and control systems for controlling a robot and other moving parts of an examination and/or processing machine, the host system would have to be able to control all of these individual systems in real time. This means that movements of the robot arm would only have to be signaled to the host system in real time, but the host system would also at the same time have to initiate measures to counteract the undesirable oscillations induced in the overall arrangement by the movements of the robot. Corresponding control signals for this purpose would have to be passed to the actuators for the active oscillation isolation system, once again in real time. However, host systems according to the prior art are not fast enough to do this.
The host systems which have been used until now therefore have the disadvantage that they are not fast enough, for example, to ensure that the effects of a movement of the robot arm on the carriage are adequately damped in real time.